M.Sc. / The Late Carboniferous to early Jurassic Karoo Supergroup of South Africa witnessed two of the “big five” Phanerozoic mass extinction events, and the formation and subsequent break-up of the supercontinent Pangea. The closure of the Permian Period witnessed the greatest biotic crisis in the history of life. What is known about the Permian-Triassic boundary (hereafter referred to as the PTB) comes almost exclusively from marine successions in Europe and Asia. Although a major extinction event has been recognized in terrestrial successions, surprisingly little is known about its effects and timing. The exact placement of the PTB in the Karoo basin is not well constrained due to shortcomings of stratigraphic methods employed to date. This has made it extremely difficult to correlate the mass extinction events in the marine and non-marine environments; however, paleomagnetic studies could provide answers to both problems of absolute placement and correlation of the PTB in non-marine and marine successions. The PTB appears to lie within an interval of reversed polarity in many marine successions. A detailed magnetostratigraphic survey across the presumed PTB in the Karoo succession at localities in the north and south of the main Karoo Bain reveal two magnetic chrons, reversed followed by normal (with the boundary close to the reversal), which extends to slightly younger results from a previous study that identified an N/R pattern, thereby identifying a R/N/R pattern. The normal chron might correlate with the long basal Triassic normal polarity interval and the reversed polarity zones above and below it known from marine successions in the Alps, Russia, Pakistan and China. The PTB is thought to be situated coincident with the LAD of Dicynodon and the event bed of Ward et al. (2000), apparently above but not necessarily diachronous with a lithology change from predominantly green- to predominantly red mudstone. This placement falls within a normal polarity interval, but could conceivably have taken place at a time of reverse polarity due to delayed acquisition of magnetic remanence. The idea of an extraterrestrial impact as the cause of the end-Permian mass extinctions is strongly enhanced by a synchronous relationship between them. The configuration of the supercontinent Pangea during this time of earth history has been the matter of debate for the last three decades, with numerous alternative reconstructions to the classic Pangea A1 having been proposed for the time preceding the Jurassic. Paleomagnetic data from the Karoo allow for the definition of a new paleopole for West Gondwanaland, which prove a valuable tool for evaluating these various reconstructions. It is neither consistent with a Pangea B-type not C reconstruction for Pangea during this time interval, because of geological ambiguities. The most likely solution to the problem is that of a persistent non-dipole field contribution to the geomagnetic field during this time. Approximately 50 million years later Pangea was unambiguously in a classic Pangea A1 configuration, and life on earth suffered yet another set back. The end-Triassic mass extinction, which marks the sequence boundary between the Triassic and the Jurassic, has not received as much attention as the other four big Phanerozoic biotic disasters. In the Karoo a pronounced turnover in faunal assemblages from typical Triassic fauna to Jurassic Fauna (dinosaurs) is seen in the Elliot Formation. Magnetostratigraphic study of localities in the north and south of the Karoo Basin provided a magnetic zonation pattern for the Elliot Formation, a tool that has led to the constraining of the sequence boundary to the transition from the lower Elliot Formation to the middle Elliot and added to the hypothesis that the faunal turnover is globally synchronous. The determination of a paleolatitude for the Elliot Formation in combination with characteristically arid lithologies (eolian sandstones) provided the base for the evaluation of the paleoclimate that characterized Pangea during the Late Triassic to Early Jurassic. Key words: Karoo Basin, Magnetostratigraphy, Mass Extinction, Paleoclimate, Paleogeography, Paleomagnetism, Pangea, Permian-Triassic, Triassic-Jurassic

The Triassic Period (~252–201.5 Ma) saw a transformative radiation and reorganization of continental tetrapod diversity following the end-Permian Extinction, including an assemblage of diverse forms that do not survive the end-Triassic (herein termed the 'endemic Triassic fauna', =ETF), as well as the earliest fossil representatives of all major modern tetrapod groups (herein termed the 'Living [Triassic to Recent] Fauna', =LTF; i.e. Salientia, Caudata, Gymnophiona, Mammaliaformes, Squamata, Rhynchocephalia, Testudinata, Crocodylomorpha, and Dinosauria). With few exceptions, only the LTF assemblage survives the end-Triassic Extinction (~201.5 Ma), highlighting the Late Triassic (~227–201.5 Ma) record as essential for understanding this pivotal transition and the evolutionary and ecological origins of post-Triassic non-marine tetrapod faunas, including those of present day. Micro-microvertebrate bonebeds are arguably the best proxy for tracking continental vertebrate biodiversity, however gaps in their Late Triassic record obscure patterns and drivers of evolutionary, ecological, and environmental change during the rise of LTF communities. In my dissertation, I use new data collected from Upper Triassic microvertebrate bonebeds from North America, and particularly the Thunderstorm Ridge site (PFV 456) in Petrified Forest National Park, Arizona, U.S.A, to fill gaps in the evolutionary record of specific groups (e.g., lissamphibians and lepidosaurs), as well as the vertebrate paleocommunity record of Triassic equatorial Pangaea. My first chapter describes and analyzes an assemblage of gymnophionomorph (stem caecilian) bones from PFV 456 which represent the oldest-known caecilian fossils globally. As the oldest caecilian fossils, they provide new support for the dissorophoid temnospondyl affinities of caecilians and other living amphibians, evidence of a step-wise acquisition of caecilian anatomies associated with fossoriality, and evidence of an ancient pattern of equatorial biogeographic restriction in caecilians from the Triassic to the present day. My second chapter describes and analyzes an assemblage of lepidosauromorphs from the Late Triassic of Equatorial Pangaea, providing new insights into the step-wise evolution tooth and jaw morphologies near the divergence of living lepidosaur clades (Squamata and Rhynchocephalia), and showing evidence for the Triassic acquisition in stem squamates and non-squamate lepidosaurs of dental features conserved in living squamates. The third chapter uses apomorphy-based identifications to describe the vertebrate diversity of the Thunderstorm Ridge site (PFV 456), providing evidence for the most species rich continental vertebrate community yet-known from the Triassic, with 55 vertebrate taxa. Nearly all LTF clades are present, predating similar assemblages from the early Jurassic by over 20 million years, and indicating that the assembly of the first LTF communities by at least 220 million years ago, long before the Triassic-Jurassic Extinction event (~201.5). The presence of this exceptional diversity may be linked to the climatic and environmental settings of equatorial Pangaea during the Triassic. / Doctor of Philosophy / The Triassic Period, lasting about 50 million years from approximately 252 to 201.5 million years ago, was a period of transformation for life living on land. During the Triassic, we see the first fossil evidence for the evolution of the tetrapod (animals with a backbone and limbs) groups familiar to us from the present-day Earth, including frogs, salamanders, caecilians, mammals, lizards, the tuatara, turtles, crocodilians, and dinosaurs. Understanding the early evolution of these groups is limited by gaps in the Triassic fossil record, particularly for groups with small-bodies and delicate skeletons like frogs, salamanders, caecilians, and lizards. The poor Triassic records of these groups also limits understandings of when and where tetrapod communities resembling those of the present-day first assembled, and whether events like the Triassic-Jurassic Extinction event (~201.5 million years ago) shaped the organization of these communities. To fill these gaps, I have focused on collecting data from microvertebrate bonebeds, layers of rock that preserve the small, delicate bones of small-bodied vertebrates that are typically rare elsewhere. New microvertebrate data collected from Late Triassic rocks in North America, and particularly the 220 million year old Thunderstorm Ridge site (PFV 456) in Petrified Forest National Park, Arizona, U.S.A., provide evidence for exceptionally diverse tetrapod communities, opening a window onto the early evolution of living tetrapods and their ecological interactions. In my first chapter I describe and analyze the bones of a stem caecilian amphibian from the Thunderstorm Ridge site. These are the oldest caecilian fossils on Earth, and they provide new evidence for the evolutionary relationships, ecologies, and biogeography of these enigmatic living amphibians. In my second chapter I describe and analyze the jaws and teeth of early lizards and their close relatives from North American Late Triassic microvertebrate sites, showing that the tooth and jaw morphologies of living lizards like geckos and skinks first evolved in their Triassic relatives. In my third chapter, I describe and identify the 55 vertebrate taxa recovered from the Thunderstorm Ridge site, showing that it is the most diverse tetrapod community known from the Triassic. The diversity of early members of living tetrapod groups at Thunderstorm Ridge suggests that tetrapod communities resembling those of the present-day first assembled in the Triassic, at least 20 million years prior to the Triassic-Jurassic Extinction.

Die MOSAiC-Expedition war die größte Polarexpedition, die je durchgeführt wurde. Mehr als ein Jahr driftete das Forschungsschiff Polarstern durch den Arktischen Ozean und erhob dabei unzählige Forschungsdaten. Die Umsetzung stellte große logistische und technische Herausforderungen. Gleichzeitig setzte das Projekt Meilensteine in der Digitalisierung der MOSAiC-Daten. Das vorhandene Datenrepositorim PANGEA wurde als Datenbasis für die Abspeicherung der erhobenen und gewonnenen Daten genutzt. Das Datenmanagement hatte ein frühestmögliches Teilen der Daten zum Ziel. Außerdem stand von Anfang an das Datenmanagement als ein Teil von open science und einer frühen Datenzitierbarkeit. Ab 2023 sollen alle MOSAiC-Daten im Repositorium frei verfügbar sein. MOSAiC ist der bisher größte Anwendungsfall für das Projekt Nationale Forschungsdateninfrastruktur (NFDI). / The MOSAiC expedition was the largest polar expedition ever conducted. For more than a year, the research vessel Polarstern drifted through the Arctic Ocean collecting countless research data. The implementation posed major logistical and technical challenges. At the same time, the project set milestones in the digitization of MOSAiC data. The existing data repositoryim PANGEA was used as a database for storing the collected and acquired data. Data management aimed at sharing the data as early as possible. In addition, from the beginning, data management stood as a part of open science and early data citability. Starting in 2023, all MOSAiC data should be freely available in the repository. MOSAiC is the largest use case to date for the National Research Data Infrastructure (NFDI) project.